P130(CAS) FORMS A SIGNALING COMPLEX WITH THE ADAPTER PROTEIN CRKL IN HEMATOPOIETIC-CELLS TRANSFORMED BY THE BCR ABL ONCOGENE/

The Philadelphia chromosome (Ph) translocation generates a chimeric ty rosine kinase oncogene, BCR/ABL, which causes chronic myelogenous leuk emia (CML) and a type of acute lymphoblastic leukemia (ALL). In primar y samples from virtually all patients with CML or Ph(+)ALL, the CRKL a dapter protein is tyrosine phosphorylated and physically associated wi th p210(BCR/ABL). CRKL has one SH2 domain and two SH3 domains and is s tructurally related to c-CRK-II (CRK) and the v-Crk oncoprotein. We ha ve previously shown that CRKL, but not the related adapter protein c-C RK, is tyrosine phosphorylated in cell lines transformed by BCR/ABL, a nd that CRKL binds to BCR/ABL through the CRKL-SH3 domains. Furthermor e, the CRKL-SH2 domain has been shown to bind one or more cellular pro teins, one of which is p120(CBL). Here we demonstrate that another cel lular protein linked to BCR/ABL through the CRKL-SH2 domain is p130(CA S). p130(CAS) was found to be tyrosine phosphorylated and associated w ith CRKL in BCR/ABL expressing cell lines and in samples obtained from CML and ALL patients, but not in samples from controls. In both norma l and BCR/ABL transformed cells, p130(CAS) was detected in focal adhes ion-like structures, as was BCR/ABL. In normal cells, the focal adhesi on proteins tensin, p125(FAK), and paxillin constitutively associated with p130(CAS). However, in BCR/ABL transformed cells, the interaction between p130(CAS) and tensin was disrupted, while the associations be tween p130(CAS), p125(FAK) and paxillin were unaffected. These results suggest that the BCR/ABL oncogene could alter the function of p130(CA S) in at least three ways: tyrosine phosphorylation, inducing constitu tive binding of CRKL to a domain in p130(CAS) containing Tyr-X-X-Pro m oths (substrate domain), and disrupting the normal interaction of p130 (CAS) with the focal adhesion protein tensin. These alterations in the structure of signaling proteins in focal adhesion Like structures cou ld contribute to the known adhesion abnormalities in CML cells.